A recently conducted Phase 0 human clinical trial of riluzole (Rilutek™) demonstrated dramatic efficacy in certain melanoma patients after only 14 days of treatment. Riluzole, the only FDA approved drug to treat amyotrophic lateral sclerosis (ALS), showed clinical or radiologic evidence of tumor response in four of 12 patients with Stage III and IV melanoma, cancer with a poor prognosis and severely limited treatment options.
It is clear that the repositioned use of riluzole for melanoma or other cancers will be significantly constrained due to high levels of variability in hepatic metabolism of the drug as is the case for its clinical use for ALS. We describe here prodrugs of riluzole in order to improve the clinical efficacy of riluzole-based therapy, increase patient compliance, and relieve human suffering. Metastatic melanoma has few treatment options, and the current therapeutic standard of care is dacarbazine which is a highly cytotoxic drug with severe side effects including vomiting, headache and hair loss. Treatment with dacarbazine has a median progression-free enhancement of survival time of only 1.5 months. Riluzole (Rilutek™) is a generally non-toxic drug and currently the only FDA-approved treatment for amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease).
We have recently shown that riluzole has dramatic anti-melanoma activity in vitro cellular assays, in mice and in a Phase 0 human clinical trial. In the clinic, four of twelve melanoma patients showed significant clinical or radiologic evidence of Stage III and IV tumor response. These results, along with the mild side-effect profile that riluzole has shown among ALS patients, suggests that this drug has significant potential for use as an improved treatment for metastatic melanoma. However, the therapeutic utility of riluzole itself in ALS and eventually for melanoma is very constrained by rapid first-pass metabolism in the liver and an exceptionally high level of patient-to-patient variability in the extent of the Cyp1A2-mediated oxidative metabolism that is observed.
There is a long felt need for new treatments for melanoma that are both disease-modifying and effective in treating patients that are refractory to current treatments. The present invention addresses the need to identify new treatments for melanoma by identifying novel prodrugs of riluzole which possess enhanced stability to hepatic metabolism and are delivered into systemic circulation by oral administration. The riluzole prodrugs are cleaved to release riluzole in the plasma via either an enzymatic or general biophysical release process.